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9.2 The Process of Cellular Respiration, Summaries of Cell Biology

Oxygen is the final electron acceptor. The passing of electrons through the electron transport chain causes H+ ions to build up in the intermembrane space, ...

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Name Class Date
9.2 The Process of Cellular Respiration
Lesson Objectives
Describe what happens during glycolysis.
Describe what happens during the Krebs cycle.
Explain how high-energy electrons are used by the electron transport chain.
Identify how much ATP cellular respiration generates.
Lesson Summary
Glycolysis The word glycolysis literally means “sugar-breaking.” The end result
is 2 molecules of a 3-carbon molecule called pyruvic acid.
2 ATP molecules are used at the start of glycolysis to get the process started.
High-energy electrons are passed to the electron carrier NAD+, forming two molecules of
NADH.
4 ATP are synthesized during glycolysis for a net gain of 2 ATP.
The Krebs Cycle The second stage of cellular respiration is the Krebs cycle, which
operates only when oxygen is available. The Krebs cycle is a series of energy-extracting
reactions.
Pyruvic acid produced by glycolysis enters mitochondria. In the innermost compartment
of a mitochondrion, or the matrix, pyruvic acid molecules are broken down into carbon
dioxide and acetyl-CoA molecules.
Acetyl-CoA combines with a 4-carbon compound, producing a 6-carbon moleculecitric
acid. Energy released by the breaking and rearranging of carbon bonds is captured in
ATP, NADH, and FADH2.
The Krebs cycle produces four types of products:
high-energy electron carriers (NADH and FADH2)
carbon dioxide
2 ATP molecules (per glucose molecule)
the 4-carbon molecule needed to start the cycle again
Electron Transport and ATP Synthesis The electron transport chain uses
the high-energy electrons from glycolysis and the Krebs cycle to convert ADP into ATP.
The electron carriers produced during glycolysis and the Krebs cycle bring high-energy
electrons to the electron transport chain. Oxygen is the final electron acceptor.
The passing of electrons through the electron transport chain causes H+ ions to build up in
the intermembrane space, making it positively charged relative to the matrix.
The charge difference across the membrane forces H+ ions through channels in enzymes
known as ATP synthases. As the ATP synthases spin, a phosphate group is added to
ADP, generating ATP.
The Totals Together, glycolysis, the Krebs cycle, and the electron transport chain
generate about 36 molecules of ATP per molecule of glucose.
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9.2 The Process of Cellular Respiration

Lesson Objectives

Describe what happens during glycolysis. Describe what happens during the Krebs cycle. Explain how high-energy electrons are used by the electron transport chain. Identify how much ATP cellular respiration generates.

Lesson Summary

Glycolysis The word glycolysis literally means “sugar-breaking.” The end result

is 2 molecules of a 3-carbon molecule called pyruvic acid.

2 ATP molecules are used at the start of glycolysis to get the process started. High-energy electrons are passed to the electron carrier NAD +, forming two molecules of NADH. 4 ATP are synthesized during glycolysis for a net gain of 2 ATP.

The Krebs Cycle The second stage of cellular respiration is the Krebs cycle , which

operates only when oxygen is available. The Krebs cycle is a series of energy-extracting reactions.

Pyruvic acid produced by glycolysis enters mitochondria. In the innermost compartment of a mitochondrion, or the matrix , pyruvic acid molecules are broken down into carbon dioxide and acetyl-CoA molecules. Acetyl-CoA combines with a 4-carbon compound, producing a 6-carbon molecule—citric acid. Energy released by the breaking and rearranging of carbon bonds is captured in ATP, NADH, and FADH 2. The Krebs cycle produces four types of products:  high-energy electron carriers (NADH and FADH 2 )  carbon dioxide  2 ATP molecules (per glucose molecule)  the 4-carbon molecule needed to start the cycle again

Electron Transport and ATP Synthesis The electron transport chain uses

the high-energy electrons from glycolysis and the Krebs cycle to convert ADP into ATP.

The electron carriers produced during glycolysis and the Krebs cycle bring high-energy electrons to the electron transport chain. Oxygen is the final electron acceptor. The passing of electrons through the electron transport chain causes H+^ ions to build up in the intermembrane space, making it positively charged relative to the matrix. The charge difference across the membrane forces H

ions through channels in enzymes known as ATP synthases. As the ATP synthases spin, a phosphate group is added to ADP, generating ATP.

The Totals Together, glycolysis, the Krebs cycle, and the electron transport chain

generate about 36 molecules of ATP per molecule of glucose.

Glycolysis

1. Complete the diagram by writing on the lines provided the names and numbers of molecules used and produced during glycolysis. 2. Why is it an investment for the cell to use two ATP at the beginning of glycolysis? 3. What are two advantages of glycolysis?

THINK VISUALLY

The Totals

15. How many ATP molecules per glucose molecule does a cell gain from each of the three stages of cellular respiration? 16. Besides glucose, what other kinds of molecules can be used to produce ATP in cellular respiration? 17. Why is cellular respiration considered an efficient process? 18. Where does the heat that warms your body come from? Explain your answer.

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